Valley preps for prickly problem

MAT-SU — A Valley invasion may be imminent.

Decades of battle with mixed results in the Lower 48 may have put the spotlight on the threat of Canada thistle there, but the invasive weed has finally reached the Mat-Su, said Dave Ianson, environmental program specialist for the Palmer Soil and Water Conservation District. While it’s not time to panic, Ianson said that the disruptive weed has been confirmed in the Mat-Su is cause for concern.

“Canada thistle displaces other species of plants that would normally come in,” he said, explaining why the obnoxious plant is considered invasive. “They’re highly adaptive to disturbances. They’ll keep the native vegetation from coming in and will spread to the detriment of other species of plants.”

With the largest concentration of agriculture-based activity in Alaska, that’s important to the Mat-Su because of the Canada thistle’s potential to destroy livestock forage and farmland, Ianson said.

“Down in the Lower 48, it’s a real problem with hundreds of thousands of acres of it,” Ianson said. “We have not had it out in the Valley — until now — and we’re trying to keep it from getting any kind of establishment in the Valley.”

Local officials are on the lookout after three populations of Canada thistle were confirmed in the Valley this summer, Ianson said. One area is on the Butte behind the reindeer farm and another in the Kepler-Bradley area.

Both of those were very small patches, said Kelly Strawn, a natural resource manager for the Palmer Soil and Water Conservation District. The Butte patch had about 30 plants, while the Kepler-Bradley one had about 10.

It’s the third outbreak that caught those at the district a little off-guard, he said. That one turned out to be a fairly large patch within Palmer city limits on South Chugach Street. Folks at Alaska Family Services on Chugach Street spotted the 982-square-foot patch of offending stems through Google Earth, Strawn said.

“I wasn’t expecting a patch that large,” he said. “I thought maybe 10 to 15 plants, not 300 to 500. But it does spread rapidly, so I guess it shouldn’t be too surprising.”

What also isn’t surprising is that the Valley has now confirmed Canada thistle, Ianson said. The invasive weed has been spreading in the Anchorage area for years, he said, which means it was only a matter of time before it reached the Mat-Su. He also said it’s one of the most recognizable of the dozens of species of invasive weeds. It general, it stands 1 to 5 feet tall, with spiny leaves and a distinctive purple flower head.

“If you come anywhere near Canada thistle and you grab it, it will be a life-changing experience,” Ianson said. “If you have any doubts about Canada thistle, take your shoes off and take a walk through it, and it will be the last time you do that. … We have not had it out in the Valley (before now), and we’re trying to keep it from getting any kind of establishment in the Valley.”

Fighting the weed can also be problematic, Ianson said, which is why he and Strawn recommend property owners who discover Canada thistle on their property contact the conservation district for help removing it. That’s because simply mowing the plants down can do more harm that good, he said. The weed spreads by clinging on boots, clothing, animals, vehicle tires and anything else the prickly seeds can adhere to.

One of the options the district recommends is to remove the plants and treat the area chemically, Strawn said. Canada thistle is insidious in nature, and its seeds can sometimes lie dormant in soil for up to 20 years. So, while it may not come back in a year or two, a patch that’s simply mowed down could come back stronger and larger years later.

The Plant Conservation Alliance’s Plant Working Group in its publication “Weed’s Gone Wild: Alien Plant Invaders of Natural Areas” outlines several methods of managing Canada thistle. The alliance is a consortium of 10 federal agencies and nearly 300 non-federal cooperators. Those methods include hand-cutting, mowing, controlled burning and chemical treatment.

The choice general depends “on the level of infestation and the type of area being managed,” the publication says. “Due to its perennial nature, entire plants must be killed in order to prevent regrowth from rootstock. … Because early season burning of Canada thistle can stimulate its growth and flowering, controlled burns should be carried out late in the growing season for best effect.”

Valley landowners on the lookout for Canada thistle should watch for plants 3 to 4 feet high with thorns and a purple flower on top, Strawn said.

“It’s pretty distinguishable,” he said, adding that if you think you find some, contact the district. “We can help you manage that plant and provide you with outreach resources. Give us a call and we can take care of it. Let’s manage it before it becomes a problem.”

Contact Greg Johnson at 352-2269 or greg.johnson@frontiersman.com.